Effect of spatial positioning and semantic content in visual working memory

Working memory (WM) uses knowledge and relations to organize and store multiple individual items in a smaller set of structured units, or chunks. We investigated whether a crowd of individuals that exceeds the WM is retained and, therefore, recognized more accurately, if individuals are represented as interacting with one another –i.e., they form social chunks. Further, we asked what counts as a social chunk in WM: two individuals involved in a meaningful interaction or just spatially close and face-to-face. In three experiments with a delayed change-detection task, participants had to report whether a probe-array was the same of, or different from a sample-array featuring two or three dyads of bodies either face-to-face (facing array) or back-to-back (non-facing array). In Experiment 1, where facing dyads depicted coherent, meaningful interactions, participants were more accurate to detect changes in facing (vs. non-facing) arrays. A similar advantage was found in Experiment 2, even though facing dyads depicted no meaningful interaction. In Experiment 3, we introduced a secondary task (verbal shadowing) to increase WM load. This manipulation abolished the advantage of facing (vs. non-facing) arrays, only when facing dyads depicted no meaningful interactions. These results show that WM uses representation of interaction to chunk crowds in social groups. The mere facingness of bodies is sufficient on its own to evoke representation of interaction, thus defining a social chunk in WM; although the lack of semantic anchor makes chunking fainter and more susceptible to interference of a secondary task.